The invention relates to apparatus for calculating a total quantity of light received from a photographed scene and more particularly relates to circuitry for digitizing the light received into a pulsating electrical signal.
Electronic flash devices are known in the art in which the flash produced by a flash tube of the device is automatically terminated after a predetermined total quantity of light has been received from the photographed scene or subject. This is accomplished with the intention of causing the quantity of light reaching the film of the associated camera to be independent of the camera-to-subject distance.
Such devices have been primarily of the analog variety, however, the art has suggested the use of digital techniques to compute the total quantity of light received. The major difficulty with a digital light sensing technique is the conversion of light intensity to a proportional pulse rate since the light received is usually of short duration and large dynamic range causing errors in the conversion.